Therapy-related leukemia is a late complication of treatment with cytotoxic drugs and/or irradiation. It is a distinctive clinicopathological and cytogenetic syndrome that is usually fatal. One of the special features of this program is that the four individual projects are absolutely dependent upon patient material, since most of the questions to be addressed arise from the nature of individual patient responses. That is, why do some patients develop secondary leukemia and others not? In addition to patient enrollment, chart review, specimen collection and data acquisition, we propose again to incorporate within the original Core formal support for database coordination, statistical analysis, and computation. In addition, we propose to expand our studies on genetic susceptibility for the development of leukemia by establishing a registry of primary and secondary leukemia families in order to ascertain familial aggregations. The Patient Access core has the dual missions of specimen acquisition and data management and analysis. These functions are critical to the successful completion of the proposed investigations and necessary to support and link together the results that will come from the various laboratories. In this way, interim analyses of data may be disseminated promptly among the project investigators, and unique patient resources may be shared in the most productive manner. In order to provide an orderly access to patient material and to maintain records, we propose to continue our Core component to manage these functions as it has for the past 10 years. Requests for specific clinical materials (blood or marrow cells, tumor tissues, DNA from buccal swabs, or cell lines from specific patients or family members) will be directed by each project PI to the Core. After collection, the clinical specimens will be logged in and transported for processing and delivery to the individual projects. Data forms will be kept in secure file cabinets, and research data will be maintained in electronic files under password security.